Monolithic ultrasonic imaging devices, systems and methods

ABSTRACT

To implement a single-chip ultrasonic imaging solution, on-chip signal processing may be employed in the receive signal path to reduce data bandwidth and a high-speed serial data module may be used to move data for all received channels off-chip as digital data stream. The digitization of received signals on-chip allows advanced digital signal processing to be performed on-chip, and thus permits the full integration of an entire ultrasonic imaging system on a single semiconductor substrate. Various novel waveform generation techniques, transducer configuration and biasing methodologies, etc., are likewise disclosed. HIFU methods may additionally or alternatively be employed as a component of the “ultrasound-on-a-chip” solution disclosed herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit under 35U.S.C. §120 of U.S. patent application Ser. No. 14/208,281, filed onMar. 13, 2014 under Attorney Docket No. B1348.70006US01 and entitled“MONOLITHIC ULTRASONIC IMAGING DEVICES, SYSTEMS AND METHODS” whichclaims the benefit under 35 U.S.C. §119(e) of U.S. Provisional PatentApplication Ser. No. 61/798,851, filed on Mar. 15, 2013 under AttorneyDocket No. B1348.70006US00 and entitled “MONOLITHIC ULTRASONIC IMAGINGDEVICES, SYSTEMS AND METHODS”, both of which are incorporated herein byreference in their entireties.

FIELD

Aspects of the present disclosure relate to devices, systems, andmethods for imaging and/or or treatment (e.g., ultrasonic imaging and/ortreatment technology). For example, certain aspects of the architectureand techniques disclosed herein allow an entire ultrasonic imagingsystem to be integrated on a single semiconductor substrate.Accordingly, many of the features and methodologies described hereinrelate to a single-chip ultrasonic imaging solution, or to devices andsystems wherein at least a substantial portion of the ultrasonic imagingsystem is provided on a single chip.

BACKGROUND

Conventional ultrasound scanners have hardware configurations such aslinear scanning with beamforming for transmit and receive operationsthat limit the types of imaging algorithms that can be used for imageprocessing.

Furthermore, the cost and scalability of ultrasonic scanners has beenapproaching the limitations of the piezoelectric transducer technologycurrently dominating the industry. Piezoelectric transducers are stillmade using “dice and fill” manufacturing processes in which individualpiezoelectric elements are cut and then positioned individually on asubstrate to form the transducer. Such processes are prone to the cost,non-uniformity, and non-scalability of machining and wiring.

The problem of transporting multiple channels of analog signals from apiezoelectric transducer array to the electronics in an ultrasoundscanner has greatly limited the utility of the larger and denser arraysof transducers needed to push the resolution of ultrasound imagingforward and to enable high-quality 3D volumetric imaging.

Recent advances in the fabrication techniques of capacitivemicromachined ultrasound transducers (CMUTs) allow high qualityultrasound transducers to be fabricated in the same semiconductorfoundries that are currently driving the electronics industry. CMUTdevices also have superior bandwidth and acoustic impedance matchingcapabilities when compared to piezoelectric transducers. Also, theincreased flexibility available to design CMUT arrays enables advancedarray design techniques that can suppress imaging artifacts, improvesignal quality, and reduce channel counts. The ultrasonic imagingsolutions using CMUT arrays that have heretofore been proposed, however,employ conventional architectures and signal processing paradigms, andthus suffer severe limitations and drawbacks.

SUMMARY

The present disclosure details various aspects of a new paradigm for thedesign of a micromachined ultrasonic transducer-based ultrasonic imager.In some embodiments, on-chip signal processing may be employed in thereceive signal path, for example, to reduce data bandwidth and/or ahigh-speed serial data module may be used to move data for all receivedchannels off-chip as digital data stream. The digitization of receivedsignals on-chip according to some embodiments of the present disclosureallows advanced digital signal processing to be performed on-chip, andthus permits complete or substantially complete integration of an entireultrasonic imaging system on a single semiconductor substrate. In someembodiments, a complete “ultrasound system on a chip” solution isprovided.

In some embodiments, the devices and architectures disclosed herein maybe fully integrated with one or more sophisticated methods, such as, forexample, one or more synthetic aperture techniques. Synthetic aperturetechniques may, for example, allow the formation of high-resolutionimagery from multiple receive aperture collections.

In some embodiments, a method for processing a signal from an ultrasonictransducer element involves using a component integrated on the samesemiconductor die as the ultrasonic transducer element to convert ananalog signal corresponding to an output of the ultrasonic transducerelement into a digital signal. In some implementations, the methodfurther involves using at least one additional component integrated onthe semiconductor die to transmit data corresponding to the digitalsignal out of the semiconductor die as a high-speed serial data stream.

In other embodiments, an ultrasound device may include at least oneultrasonic transducer element and an analog-to-digital (ADC) converterintegrated on the same semiconductor die.

In some embodiments, a method for processing a signal from an ultrasonictransducer element involves using at least one component integrated onthe same semiconductor die as the ultrasonic transducer element toprocess a signal corresponding to an output of the transducer element todecouple waveforms therefrom.

In other embodiments, an ultrasound device may include at least onecomponent, integrated on the same semiconductor die as an ultrasonictransducer element, that is configured to process a signal correspondingto an output of the at least one ultrasonic transducer element todecouple waveforms therefrom.

In some embodiments, a method for configuring at least two ultrasonictransducer elements involves coupling at least one ultrasonic transducercell in one of the two transducer elements to at least one ultrasonictransducer cell in another of the two transducer elements.

In other embodiments, at least one ultrasonic transducer cell in one ofat least two ultrasonic transducer elements is coupled to at least oneultrasonic transducer cell in another of the at least two ultrasonictransducer elements.

In some embodiments, a method involves using the output of a pulser toapply a bias signal to an ultrasonic transducer element on at least someoccasions when the pulser is not being used to drive the ultrasonictransducer element so that the ultrasonic transducer element emits anultrasonic pulse.

In other embodiments, an ultrasound device includes at least oneultrasonic transducer element and a pulser, wherein the pulser isconfigured and arranged such that, on at least some occasions when theat least one transducer element is being used to sense receivedultrasonic energy, an output of the pulser is used to bias the at leastone ultrasonic transducer element.

In some embodiments, a method for biasing at least one ultrasonictransducer element integrated on a semiconductor die involves biasingthe at least one ultrasonic transducer element using a bias voltageapplied to the semiconductor die.

In other embodiments, an ultrasound device comprises at least oneultrasonic transducer element that is configured and arranged on asemiconductor die such that a bias voltage applied to the die is alsoused to bias the at least one ultrasonic transducer element.

In some embodiments, a method for biasing at least one ultrasonictransducer element involves applying a ground to a side of the at leastone ultrasonic transducer element facing a subject while the at leastone ultrasonic transducer element is being used to image or treat thesubject.

In other embodiments, an ultrasonic device is configured so that a sideof at least one ultrasonic transducer element configured to face thesubject during imaging or treatment is connected to a ground.

In some embodiments, a method involves configuring first and secondtransmit control circuits in an ultrasound device differently so that alength of a first delay between when the first control circuit receivesa transmit enable signal and when a first waveform generated by thefirst waveform generator is applied to the first pulser is differentthan a length of a second delay between when the second control circuitreceives the transmit enable signal and when a second waveform generatedby the second waveform generator is applied to the second pulser.

In other embodiments, an ultrasound device may include at least firstand second ultrasonic transducer elements and first and second transmitcontrol circuits. The first transmit control circuit may, for example,comprise a first pulser coupled to the first ultrasonic transducerelement so as to drive the first ultrasonic transducer element so thatthe first ultrasonic transducer element emits an ultrasonic pulse, afirst waveform generator coupled to the first pulser to provide a firstwaveform to the first pulser in response to receipt of a transmit enablesignal by the first transmit control circuit, and at least one firstcomponent that impacts a length of a first delay between when the firsttransmit control circuit receives the transmit enable signal and whenthe first waveform is applied to the first pulser. The second transmitcontrol circuit may, for example, comprise a second pulser coupled tothe second ultrasonic transducer element so as to drive the secondultrasonic transducer element so that the second ultrasonic transducerelement emits an ultrasonic pulse, a second waveform generator coupledto the second pulser to provide a second waveform to the second pulserin response to receipt of the transmit enable signal by the secondtransmit control circuit, and at least one second component that impactsa length of a second delay between when the second transmit controlcircuit receives the enable signal and when the second waveform isapplied to the second pulser. In some implementations, the at least onefirst component may be configured differently than the at least onesecond component, so that the length of the second delay is differentthan the length of the first delay.

In some embodiments, a method for configuring at least first and secondwaveform generators may involve using a controller to control values offirst and second configurable operational parameters of the at leastfirst and second waveform generators.

In other embodiments, a device may include at least first and secondwaveform generators and a controller. The waveform generators may beconfigured to generate waveforms for transmission by at least first andsecond corresponding ultrasonic transducer elements. The first waveformgenerator may include at least one first configurable operationalparameter, and the second waveform generator may comprise at least onesecond configurable operational parameter. The controller may beconfigured to control values of the first and second configurableoperational parameters.

In some embodiments, a method for making an ultrasound device comprisesan act of integrating digital receive circuitry on the samesemiconductor die as at least one CMOS ultrasonic transducer element.

In other embodiments, a device comprises at least one CMOS ultrasonictransducer element and digital receive circuitry formed on a singleintegrated circuit substrate.

In some embodiments, a method for making an ultrasound device involvesfabricating at least first and second ultrasonic transducer elementsabove CMOS circuitry comprising at least first and second transmitcontrol circuits and at least first and second receive control circuitscorresponding to the first and second ultrasonic transducer elements.

In other embodiments, an ultrasound device comprises at least first andsecond ultrasonic transducer elements, and CMOS circuitry disposedunderneath the at least first and second ultrasonic transducer elements,wherein the CMOS circuitry has integrated therein first and secondtransmit control circuits and first and second receive control circuitscorresponding to the first and second ultrasonic transducer elements.

In some embodiments, a method for processing a signal from an ultrasonictransducer element involves using a component integrated on the samesemiconductor die as the ultrasonic transducer element to transmit datacorresponding to an output of the ultrasonic transducer element out ofthe semiconductor die as a high-speed serial data stream.

In other embodiments, an ultrasound device comprises at least oneultrasonic transducer element integrated on a semiconductor die, and ahigh-speed serial data module configured to transmit data correspondingto an output of the ultrasonic transducer element out of thesemiconductor die as a high-speed serial data stream.

In some embodiments, a method involves using a controller to controlvalues of operational parameters of transmit and/or control circuits forat least first and second ultrasonic transducer elements integrated onthe same semiconductor die as the transmit and/or control circuits.

In other embodiments, a device includes at least first and secondultrasonic transducer elements integrated on a semiconductor die,transmit and/or control circuits, integrated on the semiconductor die,and a controller configured to control values of operational parametersof the transmit and/or control circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and embodiments of the disclosed technology will bedescribed with reference to the following figures. It should beappreciated that the figures are not necessarily drawn to scale. Itemsappearing in multiple figures are indicated by the same reference numberin all the figures in which they appear.

FIG. 1 shows an illustrative example of a monolithic ultrasound deviceembodying various aspects of the present invention;

FIGS. 2A-B show example implementations of an imaging device adapted totransmit acoustic signals and receive only pulses that are backscatteredfrom a subject;

FIGS. 3A-B show an example implementation of a system that employs apair of opposing imaging devices to image a subject;

FIG. 4A shows an illustrative example of how an individual transducerelement in a transducer array may be arranged with respect to CMOScircuitry for that element;

FIG. 4B shows an illustrative example of an ultrasound unit comprising agroup of individual ultrasound devices that can operate together underthe direction of a controller;

FIG. 5 illustrates how, in some embodiments, a single transducer elementmay fit within a larger transducer array;

FIGS. 6A-E show five different examples of how a given transducerelement within an array might be configured in some embodiments;

FIGS. 7A-C show examples of how transducer elements may be intermingledto reduce grating lobes, etc., in some embodiments;

FIGS. 8-9 illustrate examples of how transducers cells included inrespective transducer elements of an array may be coupled together toreduce grating lobes, etc., in some embodiments;

FIG. 10 is a block diagram illustrating how, in some embodiments, the TXcontrol circuit and the RX control circuit for a given transducerelement may be used either to energize the element to emit an ultrasonicpulse, or to receive and process a signal from the element representingan ultrasonic pulse sensed by it;

FIG. 11A illustrates an embodiment of an ultrasound device in whichdigital processing of a received signal may be performed off-chip;

FIG. 11B illustrates an embodiment of an ultrasound device in which awaveform generator and some or all of the other digital circuitry may belocated off-chip;

FIG. 12A-B show examples of circuitry that may be included in each TXcontrol circuit, in some embodiments, so as to allow for true time delayand amplitude control at every transmit location of the transducerarray(s);

FIG. 13A shows an illustrative example of components that may beemployed in the timing & control circuit and each TX control circuit toselectively determine values for the registers used by the waveformgenerator in the embodiments of FIGS. 12A-B;

FIG. 13B shows an example of components that may be used to selectivelydetermine values for one or more of the operational parameters used bythe TX control circuits and/or the RX control circuits

FIG. 14 shows examples of inputs and outputs for an event controller ofthe timing & control circuit that may be provided, in some embodiments,so as to control both the transmission events and the receive eventsthat occur in an ultrasound device;

FIG. 15A shows an illustrative example of a routine that may beperformed by the event controller shown in FIG. 14 so as to generate asuitable sequence of outputs for controlling transmission and/orreception events;

FIG. 15B shows an illustrative example of a routine that may be employedin connection with the embodiment of FIG. 13A to selectively determinevalues for one or more of the operational parameters used by the TXcontrol circuits and/or the RX control circuits;

FIG. 16 shows an alternative implementation of an ultrasound device inwhich a single waveform generator may be shared by two or more TXcontrol circuits;

FIGS. 17-18 and 22-28 show illustrative examples of components that maybe included within the analog processing block and the digitalprocessing block of the RX control circuit shown in FIG. 10;

FIG. 19 shows an example implementation of the timing & control circuitshown in FIG. 1;

FIG. 20 shows an example implementation of the clock generation circuitshown in FIG. 19;

FIG. 21 shows an illustrative example of components that may be includedin the multiplexed digital processing block of the signalconditioning/processing circuit shown in FIG. 10;

FIGS. 29-30 illustrate examples of techniques for biasing transducerelements in an array or other arrangement;

FIG. 31 shows examples of components that may be included in themultiplexed digital processing block of the signalconditioning/processing circuit shown in FIG. 10;

FIGS. 32A-B illustrate embodiments in which some or all of waveformremoval circuit and/or software, image formation circuit and/orsoftware, and/or backend processing circuit and/or software may belocated off-chip;

FIG. 33 shows an example of a high voltage NMOS and PMOS layout that maybe used in some embodiments;

FIG. 34 shows an example of a very high voltage NMOS and PMOS layoutthat may be used in some embodiments;

FIG. 35 shows an example of a high voltage NMOS and PMOS bidirectionalor cascoding layout that may be used in some embodiments;

FIG. 36 shows an example of a very high voltage NMOS and PMOSbidirectional or cascoding layout that may be used in some embodiments;

FIG. 37 shows an example of a pulser using a high voltage NMOS and PMOSlayout with a high voltage switch that may be used in some embodiments;

FIGS. 38A and 38B show examples of double and quadruple voltage pulsedrivers, respectively, that may be used in some embodiments;

FIGS. 39A-B show an example of a pulser that does not employ a receiveisolation switch, which may be used in some embodiments;

FIGS. 40A and 40B show an example of a time-interleaved single slopeanalog-to-digital converter (ADC) and the operation thereof,respectively, that, in some embodiments, may be employed as one or moreof the ADCs reference herein;

FIG. 41 shows an example of a time interleaved sample and hold circuitthat may be employed in some embodiments; and

FIGS. 42A and 42B show an example of a time shared high speed ADC andthe operation thereof, respectively, that, in some embodiments, may beemployed as one or more of the ADCs referenced herein.

DETAILED DESCRIPTION

Some embodiments of the present disclosure provide new apparatuses,systems, and methods that leverage the benefits of CMUT technology andpush the forefront of ultrasound image formation processing inultrasonic scanners. In some embodiments, a robust and highly integratedultrasound “system on a chip” is provided with direct integration withultrasonic transducer arrays fabricated on the same die as a fullydigital ultrasound front-end. According to some aspects of the presentdisclosure, this architecture may allow sufficient access to fullydigitized channel data to permit the use of state-of-the-art,off-the-shelf compute platforms for performing sophisticated imageformation algorithms.

Previous efforts in this area to a large degree have either been focusedon tight integration of standard ultrasound architecture—by designingASICs capable of performing standard beamforming, but not more advancedtechniques—or focused on implementation of advanced imaging techniques,typically creating expensive devices lacking scalable integratedtechnologies. The present disclosure addresses both of these issues byproviding a unique, cost-effective, and scalable integrated ultrasoundplatform-on-a-chip that is sufficiently robust for advanced imagingapplications.

Moving beyond standard beamforming methods requires an architecture thatcan support more than just the transmission of time-delayed pulses. Thefull flexibility to implement advanced waveform coding techniquesrequires dedicated system resources for each element in a transducerarray. The present disclosure overcomes this limitation with, forexample, a novel waveform generator. In some embodiments, integratedcircuitry uniquely enables this waveform generator to control amulti-level (e.g., 3 or more level) pulser and provides the capabilityto implement many advanced ultrasound techniques in subsequentprocessing—a feature that has not been previously achieved in a fullyintegrated transducer/CMOS configuration.

Often, ultrasound receiver architectures need to reduce the databandwidth from multiple channels. One way to do this in conventionalultrasound is to use standard beamforming methods. This operation isirreversible and is not compatible with many more advanced ultrasoundimage reconstruction techniques. In many cases, the full channel datarates may exceed the bandwidth of a system's external digital link. Someembodiments disclosed herein employ a novel architecture that providesthe flexibility to use the full channel data in a way that enables anunprecedented level of control of the data rates for the data leavingthe chip.

The integrated circuit detailed herein is uniquely designed for anintegrated ultrasound imaging device. The CMOS contacts facilitatedirect wafer bonding, sacrificial release, flip-chip bonding, and/orother techniques for establishing interconnections to ultrasoundtransducing elements.

The aspects and embodiments described above, as well as additionalaspects and embodiments, are described further below. These aspectsand/or embodiments may be used individually, all together, or in anycombination of two or more, as the disclosure is not limited in thisrespect.

FIG. 1 shows an illustrative example of a monolithic ultrasound device100 embodying various aspects of the present invention. As shown, thedevice 100 may include one or more transducer arrangements (e.g.,arrays) 102, a transmit (TX) control circuit 104, a receive (RX) controlcircuit 106, a timing & control circuit 108, a signalconditioning/processing circuit 110, a power management circuit 118,and/or a high-intensity focused ultrasound (HIFU) controller 120. In theembodiment shown, all of the illustrated elements are formed on a singlesemiconductor die 112. It should be appreciated, however, that inalternative embodiments one or more of the illustrated elements may beinstead located off-chip, as discussed in more detail below. Inaddition, although the illustrated example shows both a TX controlcircuit 104 and an RX control circuit 106, in alternative embodiments(also discussed in more detail below) only a TX control circuit or onlyan RX control circuit may be employed. For example, such embodiments maybe employed in a circumstance where one or more transmission-onlydevices 100 are used to transmit acoustic signals and one or morereception-only devices 100 are used to receive acoustic signals thathave been transmitted through or reflected by a subject beingultrasonically imaged.

It should be appreciated that communication between one or more of theillustrated components may be performed in any of numerous ways. In someembodiments, for example, one or more high-speed busses (not shown),such as that employed by a unified Northbridge, may be used to allowhigh-speed intra-chip communication or communication with one or moreoff-chip components.

The one or more transducer arrays 102 may take on any of numerous forms,and aspects of the present technology do not necessarily require the useof any particular type or arrangement of transducer cells or transducerelements. Indeed, although the term “array” is used in this description,it should be appreciated that in some embodiments the transducerelements may not be organized in an array and may instead be arranged insome non-array fashion. In various embodiments, each of the transducerelements in the array 102 may, for example, include one or more CMUTs,one or more CMOS ultrasonic transducers (CUTs), and/or one or more othersuitable ultrasonic transducer cells. In some embodiments, thetransducer elements 304 of each transducer array 102 may be formed onthe same chip as the electronics of the TX control circuit 104 and/or RXcontrol circuit 106. Numerous examples of ultrasonic transducer cells,elements, and arrangements (e.g., arrays), as well as methods ofintegrating such devices with underlying CMOS circuitry, are discussedin detail in U.S. application Ser. No. 61/794,744, entitledCOMPLEMENTARY METAL OXIDE SEMICONDUCTOR (CMOS) ULTRASONIC TRANSDUCERSAND METHODS FOR FORMING THE SAME, bearing attorney docket No.B1348.70007US00 and filed on Mar. 15, 2013, the entire disclosure ofwhich is incorporated herein by reference.

A CUT may, for example, include a cavity formed in a CMOS wafer, with amembrane overlying the cavity, and in some embodiments sealing thecavity. Electrodes may be provided to create a transducer cell from thecovered cavity structure. The CMOS wafer may include integratedcircuitry to which the transducer cell may be connected. The transducercell and CMOS wafer may be monolithically integrated, thus forming anintegrated ultrasonic transducer cell and integrated circuit on a singlesubstrate (the CMOS wafer).

The TX control circuit 104 (if included) may, for example, generatepulses that drive the individual elements of, or one or more groups ofelements within, the transducer array(s) 102 so as to generate acousticsignals to be used for imaging. The RX control circuit 106 (ifincluded), on the other hand, may receive and process electronic signalsgenerated by the individual elements of the transducer array(s) 102 whenacoustic signals impinge upon such elements.

In some embodiments, the timing & control circuit 108 may, for example,be responsible for generating all timing and control signals that areused to synchronize and coordinate the operation of the other elementsin the device 100. In the example shown, the timing & control circuit108 is driven by a single clock signal CLK supplied to an input port116. The clock signal CLK may, for example, be a high-frequency clockused to drive one or more of the on-chip circuit components. In someembodiments, the clock signal CLK may, for example, be a 1.5625 GHz or2.5 GHz clock used to drive a high-speed serial output device (not shownin FIG. 1) in the signal conditioning/processing circuit 110, or a 20Mhz or 40 MHz clock used to drive other digital components on the die112, and the timing & control circuit 108 may divide or multiply theclock CLK, as necessary, to drive other components on the die 112. Inother embodiments, two or more clocks of different frequencies (such asthose referenced above) may be separately supplied to the timing &control circuit 108 from an off-chip source. An illustrative example ofa suitable clock generation circuit 1904 that may be included within thetiming & control circuit 108 is discussed below in connection with FIGS.19 and 20.

The power management circuit 118 may, for example, be responsible forconverting one or more input voltages V_(IN) from an off-chip sourceinto voltages needed to carry out operation of the chip, and forotherwise managing power consumption within the device 100. In someembodiments, for example, a single voltage (e.g., 12V, 80V, 100V, 120V,etc.) may be supplied to the chip and the power management circuit 118may step that voltage up or down, as necessary, using a charge pumpcircuit or via some other DC-to-DC voltage conversion mechanism. Inother embodiments, multiple different voltages may be suppliedseparately to the power management circuit 118 for processing and/ordistribution to the other on-chip components.

As shown in FIG. 1, in some embodiments, a HIFU controller 120 may beintegrated on the die 112 so as to enable the generation of HIFU signalsvia one or more elements of the transducer array(s) 102. In otherembodiments, a HIFU controller for driving the transducer array(s) 102may be located off-chip, or even within a device separate from thedevice 100. That is, aspects of the present disclosure relate toprovision of ultrasound-on-a-chip HIFU systems, with and withoutultrasound imaging capability. It should be appreciated, however, thatsome embodiments may not have any HIFU capabilities and thus may notinclude a HIFU controller 120.

Moreover, it should be appreciated that the HIFU controller 120 may notrepresent distinct circuitry in those embodiments providing HIFUfunctionality. For example, in some embodiments, the remaining circuitryof FIG. 1 (other than the HIFU controller 120) may be suitable toprovide ultrasound imaging functionality and/or HIFU, i.e., in someembodiments the same shared circuitry may be operated as an imagingsystem and/or for HIFU. Whether or not imaging or HIFU functionality isexhibited may depend on the power provided to the system. HIFU typicallyoperates at higher powers than ultrasound imaging. Thus, providing thesystem a first power level (or voltage) appropriate for imagingapplications may cause the system to operate as an imaging system,whereas providing a higher power level (or voltage) may cause the systemto operate for HIFU. Such power management may be provided by off-chipcontrol circuitry in some embodiments.

In addition to using different power levels, imaging and HIFUapplications may utilize different waveforms. Thus, waveform generationcircuitry may be used to provide suitable waveforms for operating thesystem as either an imaging system or a HIFU system.

In some embodiments, the system may operate as both an imaging systemand a HIFU system (e.g., capable of providing image-guided HIFU). Insome such embodiments, the same on-chip circuitry may be utilized toprovide both functions, with suitable timing sequences used to controlthe operation between the two modalities. Additional details withrespect to HIFU implementations and operational features that may beemployed in the various embodiments set forth in the present disclosureare described in co-pending and co-owned U.S. patent application Ser.No. 13/654,337, entitled TRANSMISSIVE IMAGING AND RELATED APPARATUS ANDMETHODS, filed Oct. 17, 2012, the entire contents of which isincorporated herein by reference.

In the example shown, one or more output ports 114 may output ahigh-speed serial data stream generated by one or more components of thesignal conditioning/processing circuit 110. Such data streams may, forexample, be generated by one or more USB 3.0 modules, and/or one or more10 GB, 40 GB, or 100 GB Ethernet modules, integrated on the die 112. Insome embodiments, the signal stream produced on output port 114 can befed to a computer, tablet, or smartphone for the generation and/ordisplay of 2-dimensional, 3-dimensional, and/or tomographic images. Inembodiments in which image formation capabilities are incorporated inthe signal conditioning/processing circuit 110 (as explained furtherbelow), even relatively low-power devices, such as smartphones ortablets which have only a limited amount of processing power and memoryavailable for application execution, can display images using only aserial data stream from the output port 114. Examples of high-speedserial data modules and other components that may be included in thesignal conditioning/processing circuit 110 are discussed in more detailbelow in connection with FIGS. 21 and 31. As noted above, the use ofon-chip analog-to-digital conversion and a high-speed serial data linkto offload a digital data stream is one of the features that helpsfacilitate an “ultrasound on a chip” solution according to someembodiments of the present disclosure.

Devices 100 such as that shown in FIG. 1 may be used in any of a numberof imaging and/or treatment (e.g., HIFU) applications, and theparticular examples discussed herein should not be viewed as limiting.In one illustrative implementation, for example, an imaging deviceincluding an N×M planar or substantially planar array of CMUT elementsmay itself be used to acquire an ultrasonic image of a subject, e.g., aperson's abdomen, by energizing some or all of the elements in thearray(s) 102 (either together or individually) during one or moretransmit phases, and receiving and processing signals generated by someor all of the elements in the array(s) 102 during one or more receivephases, such that during each receive phase the CMUT elements senseacoustic signals reflected by the subject. In other implementations,some of the elements in the array(s) 102 may be used only to transmitacoustic signals and other elements in the same array(s) 102 may besimultaneously used only to receive acoustic signals. Moreover, in someimplementations, a single imaging device may include a P×Q array ofindividual devices, or a P×Q array of individual N×M planar arrays ofCMUT elements, which components can be operated in parallel,sequentially, or according to some other timing scheme so as to allowdata to be accumulated from a larger number of CMUT elements than can beembodied in a single device 100 or on a single die 112.

In yet other implementations, a pair of imaging devices can bepositioned so as to straddle a subject, such that one or more CMUTelements in the device(s) 100 of the imaging device on one side of thesubject can sense acoustic signals generated by one or more CMUTelements in the device(s) 100 of the imaging device on the other side ofthe subject, to the extent that such pulses were not substantiallyattenuated by the subject. Moreover, in some implementations, the samedevice 100 can be used to measure both the scattering of acousticsignals from one or more of its own CMUT elements as well as thetransmission of acoustic signals from one or more of the CMUT elementsdisposed in an imaging device on the opposite side of the subject.

An illustrative example of an embodiment of an ultrasound unit 200 thatis adapted to transmit acoustic signals and receive only pulses that arebackscattered from a subject 202 is shown in FIGS. 2A-B. The ultrasoundunit 200 may, for example, comprise one or more devices 100 arranged inan array on a circuit board (not shown) and supported by a housing ofthe ultrasound unit 200. In the example implementation of FIG. 2A, ahigh-speed serial data stream from the ultrasound unit 200 may be outputto a serial port (e.g., a USB port) of a computer 204 for furtherprocessing and/or display on a screen 206 of the computer 204. Asdiscussed in more detail below, the computer 204 may or may not berequired to perform functions such as waveform removal, image formation,backend processing, etc., prior to displaying the image on thecomputer's display screen 206, depending on whether components forachieving such functionality are integrated on the die 112 of one ormore of the devices 100, or are otherwise provided for in the ultrasoundunit 200.

As shown in FIG. 2B, in other implementations, the high-speed serialdata stream from the ultrasound unit 200 may be provided to an inputport of a smartphone 208 for further processing and/or display. Becausethe processing power and memory available for application execution inthis type of device can be limited, in some embodiments, some or all ofthe data processing (e.g., waveform removal, image formation, and/orbackend processing, etc.) may be performed on the die 112 of one or moreof the device(s) 100, or otherwise, within the ultrasound unit 200. Inother embodiments, however, some or all of such data processing mayadditionally or alternatively be performed by one or more processors onthe smartphone 208.

Another example of an implementation that employs a pair of opposingultrasound units 200 is illustrated in FIGS. 3A-B. As shown in FIG. 3A,a pair of ultrasound units 200 may be arranged so as to straddle asubject 202 (the ultrasound unit 200 behind the subject 202 is notvisible in FIG. 3A) and to output a serial stream of data to a desktopcomputer or workstation 306. FIG. 3B illustrates how transducer array(s)102 of the device(s) 100 can be positioned so as to image a region 302within the subject 202. As discussed above, the individual transducerelements 304 in a given array 102 can be used to generate acousticsignals or to receive acoustic signals, or both, depending on theimaging technique and methodology that is to be employed. Any of theforegoing examples may, for example, allow 2D brightness mode (B-mode),3D B-mode, or tomographic ultrasonic imaging.

In some embodiments, the devices and architectures disclosed herein maybe fully integrated with one or more sophisticated methods, such as, forexample, one or more synthetic aperture techniques. Synthetic aperturetechniques may, for example, allow the formation of high-resolutionimagery from multiple receive aperture collections. Examples of suchtechniques include, but are not limited to (1) transmit and receive onall pairs of transducer elements (2) plane wave compounding, (3) inversescattering solutions for any transmit modes, (4) interpolation rangemigration (e.g., Stolt interpolation) or other Fourier resamplingtechniques, (5) dynamic focusing, (6) delay-and-sum, and (7) virtualsources.

Numerous examples of other configurations and implementations of arraysof ultrasonic transducer elements 304 that may additionally oralternatively be employed using device(s) 100 such as those disclosedherein are described in co-pending and co-owned U.S. patent applicationSer. No. 13/654,337, entitled TRANSMISSIVE IMAGING AND RELATED APPARATUSAND METHODS, filed Oct. 17, 2012, incorporated by reference above.

FIG. 4A shows an illustrative example of how an individual transducerelement 304 in a transducer array 102 may be arranged with respect toCMOS circuitry 402 (including a TX control circuit 104 and/or an RXcontrol circuit 106) for that transducer element 304. As shown, in someembodiments, each transducer element 304 may have associated with it acorresponding TX control circuit 104 and a corresponding RX controlcircuit 106. Details of example implementations of such circuits aredescribed below. In the embodiment shown in FIG. 4A, each of thetransducer elements 304 is disposed directly above its corresponding TXcontrol circuit 104 and/or RX control circuit 106 so as to, for example,facilitate interconnections, minimize cross-talk between components,minimize parasitic capacitances, etc. (As discussed previously, detailsas to how transducer cells (e.g., transducer cells 602 described below),transducer elements 304, and transducer array(s) 102 may be integratedwith or otherwise formed above CMOS circuitry in this manner areprovided in U.S. application Ser. No. 61/794,744, entitled COMPLEMENTARYMETAL OXIDE SEMICONDUCTOR (CMOS) ULTRASONIC TRANSDUCERS AND METHODS FORFORMING THE SAME, bearing attorney docket No. B1348.70007US00 and filedon Mar. 15, 2013, incorporated by reference above.)

It should be appreciated, however, that in other embodiments one or moreof the transducer elements 304 may be otherwise arranged with respect toone or more TX control circuits 104 and/or one or more RX controlcircuits 106, so as to achieve other benefits or advantages. As notedabove, moreover, it should be appreciated that, in some embodiments,some or all of the components of the TX control circuit 104 and/or theRX control circuit 106 may be omitted from the die 112, the device 100,and/or the ultrasound unit 200. In certain implementations, for example,the functionality of the TX control circuit 104 and/or the RX controlcircuit 106 may be performed by a different chip or even a differentdevice, e.g., a computer.

FIG. 4B shows an illustrative example of an ultrasound unit 200comprising a group of individual ultrasound devices 100 a-100 d that canoperate together under the direction of a controller 406. The ultrasounddevices 100 a-100 d may be of the type described herein for device 100,may be an ultrasound-on-a-chip device in some embodiments, or may beother ultrasound devices. In some embodiments, each of devices 100 a-100d may be a single chip device including ultrasound transducers andintegrated circuitry.

Moreover, the devices 100 a-100 d may be the same as each other ordifferent types of devices. For example, in some embodiments, thedevices 100 a-100 d may all provide the same functionality (e.g.,ultrasound imaging functionality). In some embodiments, one or more ofthe devices 100 a-100 d may be configured as ultrasound imaging devicesand one or more may be configured as HIFU devices. In some embodiments,one or more of the devices 100 a-100 d may be controllable to operate aseither an imaging device or a HIFU device, or both.

It should be appreciated that any number of individual devices 100 maybe arranged in an array of two, four, eight, sixteen, or any otherquantity, so as to form a larger area that can be used to emit and/ordetect ultrasonic energy. Thus, the four illustrated devices 100 a-100 drepresent a non-limiting example. In some such embodiments in whichmultiple devices 100 a-100 d are coupled as shown, the devices 100 a-100d may be packaged within a common package or housing, may be disposed ona common substrate (e.g., a board or interposer), or may be mechanicallycoupled in any suitable manner.

An example of a clock generation circuit 1904 that may be included onthe dies 112 of individual devices 100 in some embodiments so as toallow the operation of multiple devices 100 a-100 d to be synchronizedis described below in connection with FIGS. 19 and 20.

FIG. 5 illustrates how, in some embodiments, a single transducer element304 may fit within a larger transducer array 102. FIGS. 6A-E show fivedifferent examples of how a given transducer element 304 comprised ofcircular transducer cells 602 within an array 102 might be configured insome embodiments. As shown in FIG. 6A, in some embodiments, eachtransducer element 304 in an array 102 may include only a singletransducer cell 602 (e.g., a single CUT or CMUT). As shown in FIGS.6B-E, in other embodiments, each transducer element 304 in an array 102may include a group of individual transducer cells 602 (e.g., CUTs orCMUTs). Other possible configurations of transducer elements 304 includetrapezoidal elements, triangular elements, hexagonal elements, octagonalelements, etc. Similarly, each transducer cell 602 (e.g., CUT or CMUT)making up a given transducer element 304 may itself take on any of theaforementioned geometric shapes, such that a given transducer element304 may, for example, include one or more square transducer cells 602,rectangular transducer cells 602, circular transducer cells 602,asterisk-shaped transducer cells 602, trapezoidal transducer cells 602,triangular transducer cells 602, hexagonal transducer cells 602, and/oroctagonal transducer cells 602, etc.

In some embodiments, at least two of (e.g., all) of the transducer cells602 within each given transducer element 304 act as a unit and togethergenerate outgoing ultrasonic pulses in response to the output of thesame pulser (described below) and/or together receive incidentultrasonic pulses and drive the same analog reception circuitry. Whenmultiple transducer cells 602 are included in each transducer element304, the individual transducer cells 602 may be arranged in any ofnumerous patterns, with the particular pattern being chosen so as tooptimize the various performance parameters, e.g., directivity,signal-to-noise ratio (SNR), field of view, etc., for a givenapplication. In some embodiments in which CUTs are used as transducercells 602, an individual transducer cell 602 may, for example, be on theorder of about 20-110 μm wide, and have a membrane thickness of about0.5-1.0 μm, and an individual transducer element 304 may have a depth onthe order of about 0.1-2.0 μm, and have a diameter of about 0.1 mm-3 mm,or any values in between. These are only illustrative examples ofpossible dimensions, however, and greater and lesser dimensions arepossible and contemplated.

As described, for example, in Bavaro, V., et al., “Element Shape Designof 2-D CMUT Arrays for Reducing Grating Lobes, IEEE Transactions onUltrasonics, Ferroelectrics, and Frequency Control, Vol. 55, No. 2,February 2008, which is incorporated by reference in its entirety, it ispossible to select the shape of and interrelationships among transducerelements 304 so as to optimize the performance parameters of atransducer array 102. Embodiments of the ultrasonic devices describedherein may employ such techniques. FIGS. 7A-B show illustrative examplesin which the transducer cells 602 (e.g., CUTs or CMUTs) ofasterisk-shaped transducer elements 304 are intermingled, and FIG. 7Cshows an illustrative example in which the transducer cells 602 ofcircular-shaped transducer elements 306 are intermingled, so as toachieve advantages such as the reduction of grating lobes.

In some embodiments, a similar effect of reducing grating lobes, etc.,can be achieved, either in addition to or in lieu of interminglingtransducer elements 304 in the array 102, by coupling one or moretransducer cells 602 in a given transducer element 304 with one or moretransducer cells 602 in one or more adjacent or nearby transducerelements 304. By using such a technique, better use of the totaltransducer area can be attained because a given transducer cell 602 neednot belong to only a single transducer element 304 and can instead beshared by multiple transducer elements 304. This cell sharing techniquemay, in some embodiments, be combined with an apodization technique inwhich some transducer cells 602 in a transducer element 304 are causedto radiate less power than other transducer cells 602 in the sameelement.

An illustrative example of a suitable cell-sharing technique is shown inFIG. 8. In this example, transducer cells 602 (e.g., CUTs or CMUTs) atthe peripheries of transducer elements 304 are coupled to one anothervia coupling elements 802. In some embodiments, the coupling elements802 may, for example, comprise polysilicon resistors. In otherimplementations, the coupling elements 802 may additionally oralternatively comprise capacitive and/or inductive elements or features.For example, inductive couplings may be created between pairs oftransducer cells 602 by running conductors for to-be-coupled transducercells 602 in close proximity to one another. In some embodiments,certain transducer cells 602, e.g., the transducer cells 602 on theperiphery of the shared transducer elements 304, may additionally beoperated according to a desired apodization scheme. In the embodimentshown in FIG. 8, for example, an apodization scheme may be applied tothe transducer cells 602 that are coupled to the transduce cells 602 inother elements so that they radiate less power than the transducer cells602 that are not so coupled.

In some embodiments, it can also be advantageous for different impedancevalues to be used between different pairs of transducer cells 602,depending, for example, on the proximity of a transducer cell 602 to theperiphery of its transducer element 304. In some embodiments, forexample, pairs of transducer cells 602 that are both located on theperipheries of two transducer elements 304 may be coupled together withan impedance value that is higher than the impedance value used tocouple together pairs of transducer cells 602 for which one of thetransducer cells 602 is not on the periphery of its transducer element304. This possible configuration is illustrated in FIG. 9. As shown,transducer cells 602 a on the periphery of two transducer elements 304may be coupled together via a coupling 802 a (e.g., a polysiliconresistor) having a resistance value R1, whereas a transducer cell 602 bcloser to the center of a transducer element 304 may be coupled toanother transducer cell 602 via a coupling 802 b having a resistancevalue R2. The resistance value R2 may, for example, be greater than theresistance value R1. In some embodiments, a gradient of impedance valuesmay be employed that increases gradually from the periphery to themiddle portion of a transducer element 304. Again, such a cell sharingtechnique employing different impedance values, or a gradient ofimpedance values, may be combined with an apodization technique so asoptimize the performance of the array(s) 102 for a particularapplication.

As noted above, the above techniques for sharing and/or apodizing thetransducer elements 304 in the array(s) 102, either symmetrically orasymmetrically, and either uniformly about the perimeters, according tosome gradient, or otherwise, may be combined with the interminglingtechnique discussed above, such that transducer elements 304 may havetransducer cells 602 that are both intermingled and coupled together attheir peripheries or via a gradient of impedance values, or otherwise.

FIG. 10 is a block diagram illustrating how, in some embodiments, the TXcontrol circuit 104 and the RX control circuit 106 for a giventransducer element 304 may be used either to energize the transducerelement 304 to emit an ultrasonic pulse, or to receive and process asignal from the transducer element 304 representing an ultrasonic pulsesensed by it. In some implementations, the TX control circuit 104 may beused during a “transmission” phase, and the RX control circuit may beused during a “reception” phase that is non-overlapping with thetransmission phase. In other implementations, one of the TX controlcircuit 104 and the RX control circuit 106 may simply not be used in agiven device 100, such as when a pair of ultrasound units 200 is usedfor only transmissive imaging. As noted above, in some embodiments, adevice 100 may alternatively employ only a TX control circuit 104 oronly an RX control circuit 106, and aspects of the present technology donot necessarily require the presence of both such types of circuits. Invarious embodiments, each TX control circuit 104 and/or each RX controlcircuit 106 may be associated with a single transducer cell 602 (e.g., aCUT or CMUT), a group of two or more transducer cells 602 within asingle transducer element 304, a single transducer element 304comprising a group of transducer cells 602, a group of two or moretransducer elements 304 within an array 102, or an entire array 102 oftransducer elements 304.

In the example shown in FIG. 10, there is a separate TX control circuit104/RX control circuit 106 combination for each transducer element 304in the array(s) 102, but there is only one instance of each of thetiming & control circuit 108 and the signal conditioning/processingcircuit 110. Accordingly, in such an implementation, the timing &control circuit 108 may be responsible for synchronizing andcoordinating the operation of all of the TX control circuit 104/RXcontrol circuit 106 combinations on the die 112, and the signalconditioning/processing circuit 110 may be responsible for handlinginputs from all of the RX control circuits 106 (see element 1004 in FIG.10) on the die 112.

As shown in FIG. 10, in addition to generating and/or distributing clocksignals to drive the various digital components in the device 100, thetiming & control circuit 108 may output either an “TX enable” signal toenable the operation of each TX control circuit 104, or an “RX enable”signal to enable operation of each RX control circuit 106. In theexample shown, a switch 1002 in the RX control circuit 106 may always beopened before the TX control circuit 104 is enabled, so as to prevent anoutput of the TX control circuit 104 from driving the RX control circuit106. The switch 1002 may be closed when operation of the RX controlcircuit 106 is enabled, so as to allow the RX control circuit 106 toreceive and process a signal generated by the transducer element 304.

As shown, the TX control circuit 104 for a respective transducer element304 may include both a waveform generator 1006 and a pulser 1008. Thewaveform generator 1006 may, for example, be responsible for generatinga waveform that is to be applied to the pulser 1008, so as to cause thepulser 1008 to output a driving signal to the transducer element 304corresponding to the generated waveform.

In the example shown in FIG. 10, the RX control circuit 106 for arespective transducer element 304 includes an analog processing block1010, an analog-to-digital converter (ADC) 1012, and a digitalprocessing block 1014. The ADC 1012 may, for example, comprise a 10-bit,20 Msps, 40 Msps, or 80 Msps ADC.

After undergoing processing in the digital processing block 1014, theoutputs of all of the RX control circuits 106 on the die 112 (the numberof which, in this example, is equal to the number of transducer elements304 on the chip) are fed to a multiplexer (MUX) 1016 in the signalconditioning/processing circuit 110. The MUX 1016 multiplexes thedigital data from the various RX control circuits 106, and the output ofthe MUX 1016 is fed to a multiplexed digital processing block 1018 inthe signal conditioning/processing circuit 110, for final processingbefore the data is output from the die 112, e.g., via one or morehigh-speed serial output ports 114. Examples implementations of thevarious circuit blocks shown in FIG. 10 are discussed further below. Asexplained in more detail below, various components in the analogprocessing block 1010 and/or the digital processing block 1014 may serveto decouple waveforms from the received signal and otherwise reduce theamount of data that needs to be output from the die 112 via a high-speedserial data link or otherwise. In some embodiments, for example, one ormore components in the analog processing block 1010 and/or the digitalprocessing block 1014 may thus serve to allow the RX control circuit 106to receive transmitted and/or scattered ultrasound pressure waves withan improved signal-to-noise ratio (SNR) and in a manner compatible witha diversity of waveforms. The inclusion of such elements may thusfurther facilitate and/or enhance the disclosed “ultrasound-on-a-chip”solution in some embodiments.

Although particular components that may optionally be included in theanalog processing block 1010 are described below, it should beappreciated that digital counterparts to such analog components mayadditionally or alternatively be employed in the digital processingblock 1014. The converse is also true. That is, although particularcomponents that may optionally be included in the digital processingblock 1014 are described below, it should be appreciated that analogcounterparts to such digital components may additionally oralternatively be employed in the analog processing block 1010.

FIG. 11A illustrates an embodiment of a device 100 in which digitalprocessing of a received signal is not performed on the die 112. In someimplementations, this embodiment may be essentially identical to theembodiment of FIG. 10 in terms of its basic structure and function,except that the RX control circuits 106 might not, for example, employan ADC 1012 or a digital processing block 1014, and an on-chip signalconditioning/processing circuit 110 may be omitted. It should beappreciated, however, that in the embodiment of FIG. 11A one or morebuffers/drivers (not shown) may additionally be employed to drive theanalog signals onto output lines 1102 a-b of the die 112.

FIG. 11B illustrates an embodiment of an ultrasound device in which awaveform generator (not shown) and some or all of the other digitalcircuitry discussed herein may be located off-chip, rather than on thesemiconductor die 112. In some implementations, this embodiment may beotherwise identical to the embodiment of FIG. 10 in terms of its basicstructure and functionality. In some embodiments, the pulsers 1008 mayadditionally or alternatively be located off-chip.

FIG. 12A shows an example of circuitry that may be included in each TXcontrol circuit 104, in some embodiments, so as to allow for true timedelay and amplitude control at every transmit location of the array(s)102. In the illustrated example, the waveform generator 1006 is a chirpgenerator that includes a set of registers 1202 a that can be set tocontrol the characteristics of the chirp that is supplied to a tri-levelpulser 1008. Specifically, a phase register “θ₀” controls the startingphase of the chirp, the frequency register “f₀” controls the startingfrequency of the chirp, and the chirp rate register “r” controls therate at which the frequency of the chirp changes over time. Thecomparators 1204 a-b serve to discretize the waveform signal output byaccumulator 1206, so that the logical values D0, D1 supplied to thetri-level pulser 1008 are either “1,0,” “0,0,” or “0,1,” depending oncomparisons of the output of the accumulator 1206 to the valuesV0_(HIGH) and V1_(HIGH) in the registers 1202 a.

FIG. 12B shows an alternative embodiment of the waveform generator 1006.In the FIG. 12B embodiment, rather than using comparators 1204 a-b todiscretize the simulated sine-wave signal output by the accumulator1206, a look up table 1212 a is used to determine whether the output ofaccumulator 1206 is within a range defined by the values of V0_(HIGH)and V0_(LOW) in the registers 1202 b, and a look up table 1212 b is usedto determine whether the output of accumulator 1206 is within a rangedefined by the values of V1_(HIGH) and V1_(LOW) in the registers 1202 b.

The configuration and operation of a tri-level pulser suitable for useas the pulser 1008 of FIGS. 12A-B according to some embodiments, as wellas the benefits of employing such a pulser to drive a CMUT element, aredescribed in Kailiang, C, “Ultrasonic Imaging Front-End Design for CMUT:A 3-Level 30 Vpp Pulse-Shaping Pulser with Improved Efficiency and aNoise-Optimized Receiver,” IEEE Asian Solid-State Circuits Conference,”Nov. 12-14, 2012/Kobe, Japan, which is incorporated herein by referencein its entirety. Those details will therefore not be repeated here.

In the example embodiments shown in FIGS. 12A-B, the TX control circuit104 is provided with three levels of control over the timing of theoutput of the pulser 1008. The coarsest level of timing control isprovided by a shift register 1208 (which, in some embodiments, may beprogrammable, e.g., via the timing & control unit 108) located at theinput of the waveform generator 1006. The next finest level of timingcontrol is provided by the settings of the values “θ₀” and “f₀” in theregisters 1202 a-b. The finest level of timing control is provided bydelay lines 1210 a-b, which may, for example, include PIN diodes thatprovide for delays on the order of about 72 picoseconds to 22nanoseconds, or any delay value in between, though lesser and greaterdelays are also possible and contemplated.

Embodiments of the waveform generator 1006 thus described allow forwideband or narrowband beamforming, coded excitation, e.g., Golay codes,Hadamard codes, Walsh codes, Cyclic Algorithm New (CAN) coding, azimuthphase coding, and/or other orthogonal waveforms, and/or may also allowthe generation of gated continuous wave (CW) or impulse generation.Numerous additional examples of waveform generation techniques andoptions are described in co-pending and co-owned U.S. patent applicationSer. No. 13/654,337, incorporated by reference above, and will thus notbe described further here.

FIG. 13A shows an illustrative example of components that may beemployed in the timing & control circuit 108 and each TX control circuit104 to selectively determine values for the registers 1202 a-b used bythe waveform generator 1006 in the embodiments of FIGS. 12A-B. As shown,each TX control circuit 104 may include an element event memory 1304that stores values for the registers 1202 a-b corresponding to each ofseveral “TX event” numbers, and the timing & control circuit 108 mayinclude an event controller 1302 that is responsible for communicatingappropriate TX event numbers to each of the TX control circuits 104 onthe die 112. With such an arrangement, the waveform supplied to eachtransducer element 304 in an array 102 can change from pulse to pulse,and by appropriately programming the event element memory 1304,complicated event sequencing, such as the excitation coding, e.g.,Azimuth coding, mentioned above, focus/planewave scanning, etc., can beachieved. Although not illustrated in FIG. 13, it should be appreciatedthat, for operation with the waveform generator embodiment of FIG. 12B,values of V0_(low) and V1_(low) may additionally be provided from theelement event memory 1304 to the waveform generator 1006.

FIG. 14 shows inputs and outputs for an event controller 1302 of thetiming & control circuit 108 that may be provided, in some embodiments,so as to control both the transmission events and the receive eventsthat occur in a ultrasound device 100. In the embodiment shown, theevent controller is provided with the parameters N_(TXSamples),N_(RXSamples), N_(TXEvents), and N_(RXEvents), and, when enabled via anenable signal “En,” generates and outputs TX and RX event numbers, aswell as TX and RX enable signals, in response to an input clock “Clk.”

FIG. 15A shows an illustrative example of a routine 1500 that may beperformed by the event controller 1302 so as to generate a suitablesequence of outputs for controlling transmission and reception events.The flowchart on the left-hand side of FIG. 15A is an abstraction of theexample routine illustrated by the flowchart on the right-hand side ofthat figure. As shown, when the enable signal “En” is high, the routinealternates between performing a TX event subroutine 1502 and an RX eventsubroutine 1504, until the enable signal “En” transitions to low. In theexample routine shown, after being enabled, the routine 1500 firstinitializes the TX and RX event numbers to “0” (step 1506), and thenproceeds with the TX event subroutine 1502 a-c. The TX event subroutine1502 causes the TX enable signal to be high for the number of samplesspecified by the N_(TXSamples) parameter (step 1502 b), and incrementsthe TX event number by one (step 1502 c) until the current TX eventnumber exceeds the value of the N_(TXEvents) parameter (step 1502 a).When the current TX event number exceeds the value of the N_(TXEvents)parameter (step 1502 a), the routine 1500 proceeds to the RX eventsubroutine 1504.

The RX event subroutine 1504 causes the RX enable signal to be high forthe number of samples specified by the N_(RXSamples) parameter (step1504 b), and increments the RX event number by one (step 1504 c) untilthe current RX event number exceeds the value of the N_(RXEvents)parameter (step 1504 a). When the current RX event number exceeds thevalue of the N_(RXEvents) parameter (step 1504 a), the routine 1500returns to the step 1506, at which the TX and RX event numbers are againinitialized to “0,” before beginning the TX subroutine 1502 once again.By using a routine such as that shown in FIG. 15A, the event controller1302 is able to interact with the TX control circuits 104 in a device100 so that any number of the transducer elements 304 can fire a pulseat a time, and is able to interact with the RX control circuits 106 sothat an acquisition window can be acquired in a specified manner.

Possible operating modes of the event controller 1302 using the routine1500 include (1) single transmit event/single receive event, (2)multiple transmit events/single receive event, (3) single transmitevent/multiple receive events, and (4) multiple transmit events/multiplereceive events. In some embodiments, for example, in connection with abackscatter mode of operation, it may be desirable to follow each TXevent with a corresponding RX event, rather than cycling through anumber of TX events and then cycling through a number of RX events.Furthermore, for more complex events (e.g., a shear wave backscatterevent), it may be desirable to cycle through a number of TX eventsfollowed by a single RX event during each iteration of the subroutines1502, 1504. These are just a few possible event control methodologies,however, and other sequences of events are possible and contemplated.

FIG. 13B shows another example of components that may be used toselectively determine values for one or more of the operationalparameters used by the waveform generator 1006 in the embodiments ofFIGS. 12A-B (e.g., “θ,” “f₀,” “r,” “V0_(LOW),” “V0_(HIGH)” “V1_(HIGH),”and/or “V1_(LOW)”) and/or values for one or more operational parametersfor the RX control circuit 106, e.g., to control the LNA 1702, VGA 1704,etc. (discussed below in connection with FIGS. 17, 22, 24, 26, 27, 29,and 30). Such values may, for example, be stored in a set of “nextstate” registers 1312 a-b and a corresponding set of “current state”registers 1314 a-b for each transducer element 304.

As shown, a peripheral control module 1306, e.g., a USB 3.0 peripheralcontroller, may be integrated on the semiconductor die 112 so as toallow an external microprocessor 1308 to selectively communicate newvalues to the next state registers 1302 associated with some or all ofthe transducer elements 304 in an array 102. In some embodiments, eachgroup of state registers 1312, 1314 may be controlled by a correspondingregister control module 1310 a-b. As shown, in some embodiments, theregister control modules 1310 a-b may be daisy chained from one registercontrol module 1310 to the next.

FIG. 15B shows an example of a routine 1508 that may be followed toselectively configure the registers 1312, 1314 in some embodiments. Asshown, the microprocessor 1308 may, for example, receive an interruptsignal IRQ over the USB 3.0 link prior to each frame. Upon receivingsuch an interrupt, the microprocessor 1308 may determine whether thestate of the current registers 1314 needs to be changed for the nextevent (see step 1510). If the microprocessor 1308 determines that thestate should change, it may push a new complete sequence down the chain(see step 1512) and latch the new values into the next state registers1312. The new values in the next state registers 1312 may then belatched into the current state registers 1302 on the frame boundary (seestep 1514) for use in executing the next event (see steps 1516 and1518). The above process may then be repeated to latch any desired newvalues into the next state registers 1312. Using such a technique toselectively control operational parameters of the TX control circuit 104and/or the RX control circuit 106, may, for example reduce the requiredlocal memory requirements on the die 112, and may allow every pulse tohave a unique definition with any arbitrary combination since themicroprocessor 1308 may have fewer resource constraints than the sensor102.

FIG. 16 shows an alternative implementation of an ultrasound device 100in which a single waveform generator 1006 may be shared by two or moreTX control circuits 104. The shared waveform generator 1006 may, forexample, be included in the timing & control circuit 108. As shown,rather than using the timing & control circuit 108 to selectively enablethe TX control circuits 104 in a desired sequence, delay elements 1602may be disposed between the shared waveform generator 1006 and therespective pulsers 1008 in the TX control circuits 106, with the delayelements 1602 being selected so as to cause the output of the sharedwaveform generator 1006 to reach the respective pulsers 1008 accordingto a desired timing sequence. The delay elements 1008 may, for example,be located in the TX control circuits 104, in the timing & controlcircuit 108, or elsewhere. Using the illustrated technique, thetransducer elements 304 of an array 102 may be pulsed according to anydesired timing sequence, as determined by the delays provided by therespective delay elements 1602.

FIG. 17 shows an illustrative example of components that may be includedwithin the analog processing block 1010 and the digital processing block1014 of each RX control circuit 106 (see FIG. 10). In some embodiments,the components of the RX control circuit 106 may, for example,collectively have a bandwidth from DC to 50 MHz and provide a gain of 50dB, with a noise figure of less than 4 dB, aliased harmonic rejection of45 dB, and channel isolation of 40 dB. Such parameters are listed forillustrative purposes only and are not intended to be limiting. Otherperformance parameters are possible and contemplated.

As shown in FIG. 17, the analog processing block 1010 may, for example,include a low-noise amplifier (LNA) 1702, a variable-gain amplifier(VGA) 1704, and a low-pass filter (LPF) 1706. In some embodiments, theVGA 1704 may be adjusted, for example, via a time-gain compensation(TGC) circuit 1902 (shown in FIG. 19) included in the event controller1302 of the timing & control circuit 108. The LPF 1706 provides foranti-aliasing of the acquired signal. In some embodiments, the LPF 1706may, for example, comprise a 2^(nd) order low-pass filter having afrequency cutoff on the order of 5 MHz. Other implementations are,however, possible and contemplated. As noted above, the ADC 1012 may,for example, comprise a 10-bit, 20 Msps, 40 Msps, or 80 Msps ADC.

In the example of FIG. 17, the digital control block 1014 of the RXcontrol circuit 106 includes a digital quadrature demodulation (DQDM)circuit 1708, an averaging circuit 1714 (including an accumulator 1710and an averaging memory 1712), and an output buffer 1716. The DQDMcircuit 1708 may, for example, be configured to mix down the digitizedversion of the received signal from center frequency to baseband, andthen low-pass filter and decimate the baseband signal. An illustrativeexample of a quadrature demodulation circuit that may be employed as theDQDM 1708 is shown in FIG. 18. As shown, the DQDM 1708 may, for example,include a mixer block 1802, a low-pass filter (LPF), and a decimatorcircuit 1806. The illustrated circuit may allow for a lossless reductionof bandwidth by removing unused frequencies from the received signal,thus significantly reducing the amount of digital data that needs to beprocessed by the signal conditioning/processing circuit 110 andoffloaded from the die 112. The bandwidth reduction achieved by thesecomponents may help to facilitate and/or improve the performance of the“ultrasound-on-a-chip” embodiments described herein.

In some embodiments, it may be desirable to match the center frequency“f_(c)” of the mixer block 1802 with the frequency of interest of thetransducer cells 602 that are used in the array(s) 102. Examples ofadditional components that may, in some embodiments, be included in RXcontrol circuits 106, in addition to or in lieu of the DQDM 1708 and/orthe other components illustrated in FIG. 17 are described below inconnection with FIGS. 22-28. The averaging block 1714 in the embodimentshown (including accumulator 1710 and averaging memory 1712) functionsto average received windows of data.

FIG. 19 shows an example implementation of the timing & control circuit108. As shown, in some embodiments, the timing & control circuit 108 mayinclude both a clock generation circuit 1904, and an event controller1302. The clock generation circuit 1904 may be used, for example, togenerate some or all of the clocks used throughout the device 100. Anexample implementation of the clock generation circuit 1904 is shown inFIG. 20. As shown, in some embodiments, an external circuit 2002 may beused to generate a high-speed (e.g., 1.5625 GHz) clock, e.g., using anoscillator 2004 and a phase lock loop (PLL) 2006, that can be fed to theclock generation circuit 1904. In addition to being fed toserializer/deserializer (SerDes) circuitry 2008, the clock may bestepped down (e.g., via frequency divider circuit 2010) to a firstfrequency for use for clocking certain components on the die 112, andmay be further stepped down (e.g, via frequency divider circuit 2016) toa second frequency for use by other components on the die 112. In someembodiments, for example, the frequency divider circuit 2010 may dividethe 1.5625 GHz clock so as to yield a 40 MHz clock on the clock line2022 for use within the die 112, and the frequency divider circuit 2016may further divide the 40 MHz clock so as to yield a 20 MHz clock on theclock line 2024 for use within the die.

As shown, in some embodiments, the die 112 may have terminals 2026, 2028connected to inputs of multiplexers 2012, 2018, respectively, to acceptclock signals from external sources, and may additionally have outputterminals 2030, 2032 connected to the outputs of the multiplexers 2012,2018, respectively, to allow clock signals to be fed off-chip. Byappropriately controlling the multiplexers, this configuration can allowmultiple chips to be synchronized by daisy chaining clocks. Thus, forsome implementations, this technique allows multiple devices 100 to beextended into a fully synchronized, coherent M×N array of devices 100that can operate as a unit to image a subject.

Returning to FIG. 19, one illustrative example an event controller 1302that may be included in the timing & control circuit 108 is describedabove in connection with FIG. 13A. As shown in FIG. 19, however, in someembodiments, the event controller 1302 may additionally comprise a TGCcircuit 1902 that may be used, for example, to control the gain of theVGAs 1704 in the analog processing blocks 1010 of the RX controlcircuits 106.

FIG. 21 shows an illustrative example of components that may be includedin the multiplexed digital processing block 1018 of the signalconditioning/processing circuit 110 on the die 112. As shown, themultiplexed digital processing block 1018 may, for example, include are-quantizer 2102 and a USB 3.0 module 2104. In some embodiments, there-quantizer 2102 may, for example, perform lossy compression to providebandwidth reduction. The re-quantizer 2102 may operate in any ofnumerous ways, and aspects of the present technology do not necessarilyrequire the use of any particular type of re-quantization technique. Insome embodiments, the re-quantizer 2102 may, for example, find a maximummagnitude of the incoming signal, scale all signals up to make themaximum signal full-scale, and then throw away the lower N-bits from thesignal. In other embodiments, the re-quantizer 2102 may additionally oralternatively covert the signal to log space and keep only N bits of thesignal. In yet other embodiments, the re-quantizer 2102 may additionallyor alternatively employ Huffman coding and/or vector quantizationtechniques.

As shown in FIG. 21, one option for outputting a high-speed serial datastream from the die 112 is a USB 3.0 module. Details as to the structureand operation of such a USB 3.0 module are described, for example, inthe Universal Serial Bus Revision 3.0 Specification, available athttp://www.usb.org, the entire content of which is incorporated hereinby reference. Although FIG. 21 illustrates the use of a USB 3.0 moduleto provide a high-speed serial data stream from the chip, it should beappreciated that other data output techniques may additionally oralternatively be employed. For example, one or more 10 GB, 40 GB, or 100GB Ethernet modules may additionally or alternatively be employed. Inother embodiments, other high-speed parallel or high-speed serial dataoutput modules and/or techniques may additionally or alternatively beemployed.

FIG. 22 shows an example implementation of the RX control circuit 106that includes a matched filter 2202 that may, for example, performwaveform removal and improve the signal-to-noise ratio of the receptioncircuitry. Although labeled a “matched” filter, the filter circuit 2202may actually operate as either a matched filter or a mismatched filterso as to decouple waveforms from the received signal. The matched filter2202 may work for either linear frequency modulated (LFM) or non-LFMpulses.

An illustrative embodiment of a circuit suitable for use as the matchedfilter 2202 is shown in FIG. 23. As shown, the matched filter 2202 may,for example, include a padding circuit 2302, a fast Fouriertransformation (FFT) circuit 2304, a multiplier 2306, a low-pass filter2308, a decimator circuit 2310, and an inverse FFT circuit 2312. Ifemployed, the padding circuit 2302 may, for example, apply padding tothe incoming signal sufficient to avoid artifacts from an FFTimplementation of circular convolution.

To operate as a “matched” filter, the value of “H(ω)” applied to themultiplier 2306 should be a conjugate of the transmission waveformT_(x)(ω). In some embodiments, the filter 2202 may thus indeed operateas a “matched” filter, by applying a conjugate of the transmissionwaveform T_(x)(ω) to the multiplier 2306. In other embodiments, however,the “matched” filter 2202 may instead operate as a mismatched filter, inwhich case some value other than a conjugate of the transmissionwaveform T_(x)(ω) may be applied to the multiplier 2206.

FIG. 24 shows another example implementation of the RX control circuit106. In the FIG. 24 embodiment, the RX control circuit 106 includes adechirp circuit 2402 that can perform yet another technique to reducebandwidth by isolating signals of interest. Dechirp circuits as alsosometimes referred to as “digital ramp” or “stretch” circuits. Invarious embodiments, a dechirp circuit 2402 may be included within theanalog processing block 1010, or may be included within the digitalprocessing block 1014 of the RX, or may be included in both the analogprocessing block 1010 and the digital processing block 1014 of the RXcontrol circuit 106. Using a dechirp circuit with an LFM waveformeffectively converts time to frequency.

An example of a digital dechirp circuit 2402 is shown in FIG. 25. Asshown, the dechirp circuit 2402 may include a digital multiplier 2502, adigital low pass filter 2504, and a decimator circuit 2506. (An analogdechirp circuit—discussed below in connection with FIG. 26—would employan analog multiplier and filter, rather than a digital multiplier andfilter, and would not include the decimator circuit 2506). The“reference chirp” shown in FIG. 25 may, for example, be the same “chirp”as that generated by the waveform generator 1006 in the corresponding TXcontrol circuit 104.

FIG. 26 shows yet another example implementation of an RX controlcircuit 106. In this example, rather than using a DQDM circuit and adigital dechirp circuit in the digital processing block 1014, an analogquadrature demodulation (AQDM) circuit 2602 and an analog dechirpcircuit 2604 are included in the analog processing block 1010. In suchan embodiment, the AQDM 2602 may, for example, employ an analog mixer(not shown) and a local oscillator (not shown) to mix the incomingsignal to baseband and then employ a low-pass analog filter (not shown)to remove unwanted frequencies from the analog signal. As shown in FIG.26, two ADCs 2606 a-b (e.g., two 10-bit 10 Msps, 20 Msps, or 40 MspsADCs) may be employed in this embodiment to convert the output of theanalog dechirp circuit 2604 into a digital signal format, but each ofthe ADCs 2606 a-b may run at half the rate as the ADC 1012 employed inthe other examples, thus potentially reducing power consumption.

Still another example of an RX control circuit 106 is shown in FIG. 27.In this example, a low-pass filter 2702 and multiplexer 2704 areincluded in the digital processing block 1014, together with anaveraging block 1714. In some embodiments, the low-pass filter 2702 may,for example, include a ½ band decimating finite impulse response (FIR)filter, and its operation may be configured to minimize the number ofnon-zero taps. An illustrative example of such a FIR filter 2702 isshown in FIG. 28.

It should be appreciated that, in various embodiments, each RX controlcircuit 106 may use any of the foregoing analog and digital circuitelements either alone or in combination with any of the other describedcircuit elements, and aspects of the present technology do notnecessarily require the specific configurations and/or combinationsillustrated herein. For example, each RX control circuit 106 may, insome embodiments, include any one or more of an AQDM 2602, an analogdechirp circuit 2604, a DQDM 1708, a matched and/or unmatched filter2202, a digital dechirp circuit 2402, an averaging block 1714, and alow-pass filter 2702, in any combination and in any order with respectto the other components, provided analog-to-digital and/ordigital-to-analog conversion is performed, as necessary. Importantly,the use of any or all of the above-described bandwidth reductiontechniques may, for some embodiments, help make the“ultrasound-on-a-chip” designs described herein a practical, viable, andcommercially feasible solution.

FIG. 29 illustrates an example of a novel technique for biasing thetransducer elements 304 in an array 102. As shown, the side of each ofthe transducer elements 304 that faces the patient may be connected toground, so as to minimize risk of electric shock. The other side of eachtransducer element 304 may be connected to the output of the pulser 1008via a resistor 2902. Accordingly, each transducer element 304 is alwaysbiased via the output of the pulser 1008, regardless of whether theswitch S1 is open or closed. In some embodiments, e.g., embodimentsemploying transducer elements 304 comprising one or more CUTs or CMUTs,the bias voltage applied across the element may be on the order of 100V.

As illustrated in the accompanying timing diagram of FIG. 29, the switchS1 may be closed during a transmit operation and may be open during areceive operation. Conversely, the switch S2 may be closed during areceive operation and may be open during a transmit operation. (Notethat there is always a gap between the opening of switch S1 and theclosing of switch S2, as well as between the opening of switch S2 andthe closing of switch S1, so as to ensure the pulser 1008 does not applyan outgoing pulse to the LNA 1702 in the RX control circuit 106.)

As also shown in the timing diagram, the pulser 1008 may hold the bottomplate of the transducer element 304 at its high output level at alltimes except when it is applying a waveform pulse to its transducerelement 304, and the waveform pulse applied during the transmit phasemay be referenced from the high output level of the pulser 1008.Accordingly, each individual pulser 1008 is able to maintain an idealbias on its corresponding transducer element 304 at all times. As shownin FIG. 29, a capacitor 2904 may be placed between the switch S2 and theLNA 1702 of the RX control circuit 106 so as to block the DC bias signal(i.e., the high output of the pulser 1008) from reaching the LNA 1702during receive operations (i.e., when switch S2 is closed).

Biasing the transducer elements 304 via their respective pulsers 1008may provide benefits in some embodiments, such as reducing cross-talkthat would otherwise occur if the elements 304 were biased via a commonbus, for example.

FIG. 30 shows another illustrative example of a technique for biasingthe transducer elements 304 in an array 102. As with the embodiment ofFIG. 29, the side of the transducer element 304 facing the patient maybe grounded, and a switch S1 may be positioned between the output of thepulser 1008 and the other side of the transducer element 304. A switchS2 in this case may be positioned directly between the non-grounded sideof the transducer element 304 and the LNA 1702 of a RX control circuit106. In this example, a capacitor is not positioned between the switchS2 and the LNA 1702, thus resulting in a potentially significant savingsof real estate on the die 112 that would otherwise be consumed by suchcapacitors. In some embodiments, one of the two switches, i.e., eitherswitch S1 or switch S2 may always be closed. In transmit mode, switch S1may be closed and switch S2 may be open. Conversely, in receive mode,switch S2 may be open and switch S1 may be closed.

To create the appropriate bias voltage at the output of each pulser 1008and the input of each LNA 1702, as illustrated in FIG. 30, the entiredie 112 (except for the portion that is used to bias the other side ofthe transducer elements 304, e.g., the top metal layer of the transducerarray 102) may be biased at an optimal bias voltage for the transducerelements 304. This arrangement may thus facilitate safe high-voltagebiasing of the transducer elements 304 via both the pulsers 1008 and theLNAs 1702 at all times. In some embodiments, the power supply of thechip may be floated so that it is not grounded, and some or all of thecontrol, configuration, and communication inputs/outputs to the die 112can be isolated, e.g., using optical isolation techniques orappropriately sized capacitors, thus DC blocking the high-voltage fromleaving the chip.

FIG. 31 shows an illustrative example of components that may be includedin the multiplexed digital processing block 1018 of the signalconditioning/processing circuit 110 on the die 112, in addition to or inlieu of the components discussed above in connection with FIG. 10. Insome embodiments, one or more of the illustrated components may beintegrated on the die 112, together with some or all of the othercircuitry described herein, provided a sufficiently small process isused for the CMOS or other integrated circuit fabrication methodologythat is employed to fabricate the die 112.

In the example of FIG. 31, the signal conditioning/processing circuitry110 includes a re-quantizer module 2102, a waveform removal circuitand/or software 3102, an image formation circuit and/or software 3104, abackend processing circuit and/or software 3106, and a USB 3.0 module2104. As the re-quantizer module and USB 3.0 module, and alternativesthereto, were discussed above in connection with FIG. 21, thosecomponents will not be described further here. As shown, in someembodiments, one or more processors 3108, e.g, CPUs, GPUs, etc., and/orlarge-scale memories may be integrated on the die 112, together with theother circuitry discussed above, so as to enable some or all of thewaveform removal functionality, image formation functionality, and/orbackend processing functionality, as described below, to be implementedvia software routines executed by such components, as well as to achieveother functionality of the other components of the device 100 describedabove. Accordingly, in such embodiments, the waveform removal module3102, image formation module 3104, and/or backend processing module 3106shown in FIG. 31 may be implemented partially or entirely via softwarestored in memory either on the die 112 or in one or more off-chip memorymodules. In some embodiments, one or more high-speed buses 3110, such asthose used by a unified Northbridge chip, or similar components may beemployed to allow high-speed data exchange among the processors(s) 3108,memory modules, and/or other components either located on the die 112 ordisposed at some off-chip location. In other embodiments, some or all ofsuch functionality of the image formation module 3104, and/or backendprocessing module 3106 may additionally or alternatively be performedusing one of more dedicated circuits integrated on the die 112.

In some embodiments, the waveform removal circuit and/or software 3102may, for example, contain circuitry and/or software, similar to thatdiscussed above in connection with the RX control circuits 106, toperform deconvolution of the waveform, dechirping, FFTs, FIR filtering,matched filtering and/or mismatched filtering, etc. Any or all of theforegoing functionality may be performed, either alone or together withany of the other functionality, in any order, by the waveform removalcircuit and/or software 3102 on the die 112. Alternatively, in someembodiments, such waveform removal circuit and/or software 3102 may beseparate from the die 112 but co-located with the die 112 in anultrasound unit 200 and the same circuit board and/or in the samehousing.

In some embodiments, the image formation circuit and/or software 3104may, for example, contain circuitry and/or software configured toperform apodization, back projection and/or fast hierarchy backprojection, interpolation range migration (e.g., Stolt interpolation) orother Fourier resampling techniques, dynamic focusing techniques, and/ordelay and sum techniques, tomographic reconstruction techniques, etc.Any or all of the foregoing functionality may be performed, either aloneor together with any of the other functionality, in any order, by theimage formation circuit and/or software 3104 on the die 112. In someembodiments, the image formation circuit and/or software 3104 and thewaveform removal circuit and/or software 3102 may both be located on thedie 112. Alternatively, in some embodiments, such image formationcircuit and/or software 3104 and/or the waveform removal circuit and/orsoftware 3102 may be separate from the die 112 but co-located with thedie 112 in an ultrasound unit 200 and the same circuit board and/or inthe same housing.

In some embodiments, the backend processing circuit and/or software 3106on the die 112 may, for example, contain circuitry and/or softwareconfigured to perform down-range and/or cross-range autofocusing,frequency dispersion compensation, non-linear apodization, remapping,compression, denoising, compounding, Doppler, elastography,spectroscopy, and/or basis pursuit techniques, etc. Any or all of theforegoing functionality may be performed, either alone or together withany of the other functionality, in any order, by the back-end processingcircuit and/or software 3106 on the die 112. In some embodiments, thebackend processing circuit and/or software 3106, the image formationcircuit and/or software 3104, and/or the waveform removal circuit and/orsoftware 3102 may all three be located on the die 112. Alternatively, insome embodiments, such backend processing circuit and/or software 3106,image formation circuit and/or software 3104, and/or the waveformremoval circuit and/or software 3102 may be separate from the die 112but co-located with the die 112 in an ultrasound unit 200 and the samecircuit board and/or in the same housing.

In some embodiments, memory used to achieve some or all of theabove-described functionality may be located on-chip, i.e., on the die112. In other embodiments, however, some or all of the memory used toimplement some or all of the described functionality may be locatedoff-chip, with the remainder of the circuitry, software, and/or othercomponents being located on the die 112.

Although not separately shown, it should be appreciated that, in someembodiments, some or all of the operational parameters of the timing &control circuit 108, the individual TX control circuits 104, theindividual RX control circuits 106 and/or the signal processing/controlcircuit 110 may be selectively configured or programmed via one or moreserial or parallel input ports to the die 112. For example, the timing &control circuit 110 may include a set of externally-writable registerscontaining values for the parameters N_(TXSamples), N_(TXEvents),N_(RXSamples), and/or N_(RXEvents) discussed above in connection withFIGS. 14 and 15; the registers 1202 of the TX control circuits 104discussed above in connection with FIGS. 12A-B may be selectivelyprogrammed via one or more input ports; operational parameters of one ormore of the components of the RX control circuit 106 discussed above inconnection with FIGS. 17, 18, and 22-28 may be selectively programmedvia one or more input ports; operational parameters for one or more ofthe re-quantizer circuit 2102 and/or USB 3.0 circuit 2104 or othermodules discussed above in connection with FIG. 21 may be programmed viaone or more input ports; and/or operational parameters for one or moreof the waveform removal circuit 3102, image formation circuit 3104,and/or backend processing circuit 3106 discussed above in connectionwith FIG. 31 may be programmed via one or more input ports.

FIGS. 32A-B illustrate embodiments in which some or all of the waveformremoval circuit and/or software 3102, the image formation circuit and/orsoftware 3104, and/or the backend processing circuit and/or software3106 may be located off-chip, e.g., on a computing device 3202, 3206separate from the device 100. As shown in FIG. 32A, on a computingdevice 3202 not including one or more field-programmable gate arrays(FPGAs) 3208, waveform removal may be performed by software executed bythe processor 3204 of the computing device 3202, together with imageformation and backend processing functions. As shown in FIG. 32B, on acomputing device 3206 that includes one or more FPGAs 3208, waveformprocessing functionality may be performed by the FPGA(s) 3208 inaddition to or in lieu of the processor 3204 of the computing device3206 performing such functionality.

As described herein, aspects of the present disclosure provide forintegration of ultrasonic transducer elements with circuitry on a singlechip. The ultrasonic transducer elements may be used for ultrasoundimaging applications, HIFU, or both. It should be appreciated that suchelements may operate at voltages higher than those conventionally usedfor CMOS integrated circuitry, e.g., higher than voltages typicallysupported by deep submicron CMOS circuitry. For example, such ultrasonictransducer elements may operate at voltages between 20 V and 120 V,between 30 V and 80 V, between 40 V and 60 V, at any voltage withinthose ranges, or at any other suitable voltages. HIFU applications mayutilize higher voltages than ultrasound imaging applications.

Thus, integration of ultrasonic transducer elements with circuitry on asingle chip may be facilitated by making such circuitry compatible withhigher voltages than traditionally used for CMOS integrated circuitry,i.e., by operating standard CMOS deep submicron circuitry at higher thancustomary voltages.

There are two main issues that can limit the operating voltage of NMOSand PMOS devices in CMOS circuits: (1) gate oxide breakdown, and (2)source and drain (diffusion) breakdown. In many designs, diffusionbreakdown is the first limitation, in that the diffusion is specificallyengineered in field effect transistors (FETs) to break down before thegate oxide so as to protect the gate oxide. To increase the diffusionbreakdown voltage, the relative concentrations in the source/drainregions to the substrate should be adequate. In some embodiments, lowerdoping levels in the source and drain regions may increase breakdownvoltage.

With respect to gate oxide breakdown, an excessive electric field maystress the gate oxide, leading to rupture or gate leakage current. Toincrease the gate-to-drain or gate-to-source breakdown voltage, themaximum electric field should be reduced.

Various methods can be used to make high-voltage CMOS circuits. Suchmethods may, for example, be implemented at the level of mask logicoperations and device layout. The standard diffusion junction in NMOStechnologies is N+ degenerately doped to P-well retrograde dopedtypically on the order of 10¹⁷ to 10¹⁸ dopants/cm³. A 3V devicetypically breaks down at 6 volts. The source and drain may, for example,be defined by the same implant that dopes the poly-Si gate. This isgenerally called a self-aligned transistor.

The standard gate-to-drain interface is a Lightly Doped Drain (LDD). TheLDD may, for example, be doped to reduce the electric field but may beminimized in size in order to keep device length large enough tomaintain gate control.

CMOS circuitry may, for example, be turned into high-voltage CMOScircuitry by changing the diffusion scheme. For example, a mask-alignedsource and drain using N-well and P-well regions may be employed. ForNMOS implementations, the diffusion may be changed to N-wellsource/drain with P-substrate. For PMOS, the diffusion may be changed toP-well source/drain regions with N-Well and Deep N-well. The source anddrains may be defined by Shallow Trench Isolation (STI). Alternatively,for larger voltages, the source and drains may be defined by gap spaceand thermal diffusion.

Examples of circuit layouts and associated structures that may be usedto implement high-voltage CMOS circuits in the various embodiments setforth in this disclosure are shown in FIGS. 33-42.

FIG. 33 shows an example of a high voltage NMOS 3301 a and PMOS 3301 blayout that may be used in some embodiments, for example to provide highvoltages a deep submicron nodes. The reference numerals set forth inFIG. 33 correspond to the following features and/or characteristics ofthe illustrated layout: 3302—Large junction breakdown due to N-well(NW)/P-substrate (Psub 3303); 3304—Reduced E-field due to LDD;3306—Large junction breakdown due to P-well (PW)/NW; and 3308—ReducedE-field due to LDD.

FIG. 34 shows an example of a very high voltage NMOS 3401 a and PMOS3401 b layout that may be used in some embodiments. The referencenumerals set forth in FIG. 34 correspond to the following featuresand/or characteristics of the illustrated layout: 3402—Mask defineddoping for N+ implant; 3404—Thermally diffused PW/Psub; 3406—Thermallydiffused NW/Psub; 3408—Mask defined doping for P+ implant;3410—Thermally diffused NW/Psub; and 3412—Thermally diffused PW/Psub.

FIG. 35 shows an example of a high voltage NMOS 3501 a and PMOS 3501 bbidirectional or cascoding layout that may be used in some embodiments.The reference numerals set forth in FIG. 35 correspond to the followingfeatures and/or characteristics of the illustrated layout: 3502—N-wellsource and source gate extension; 3504—N-well drain and gate extension;3506—P-Well source and source gate extension; and 3508—P-well drain andgate extension.

FIG. 36 shows an example of a very high voltage NMOS 3601 a and PMOS3601 b bidirectional or cascoding layout that may be used in someembodiments. The reference numerals set forth in FIG. 36 correspond tothe following features and/or characteristics of the illustrated layout:3602, 3604—Thermally diffused source and drain in Psub; 3606—OptionalP-well gate implant for threshold increase; 3608, 3610—Thermallydiffused source and drain in Psub; and 3612—Optional N-well gate implantfor threshold increase.

FIG. 37 shows an example of a pulser using a high voltage NMOS and PMOSlayout with a high voltage switch that may be used in some embodiments.The reference numerals set forth in FIG. 37 correspond to the followingfeatures and/or characteristics of the illustrated layout: 3702—CUT;3704 and 3706 represent transistor switches. To disable the pulser, setTxp=0, Txn=1, and then set Txn=0 (PMOS will hold state as long as c nodestays within low voltage rails). 3708 represents an Enable switch forreceive an enable signal rx_en to isolate from high voltage. Thetransistors may have thick channels as illustrated by the thick gatelines in the figure, which signifies a high voltage (HV) device.

FIGS. 38A and 38B show examples of a double and quadruple voltage pulsedrivers, respectively, that may be used in some embodiments. Thereference numerals set forth in FIGS. 38A and 38B correspond to thefollowing features and/or characteristics of the illustrated layout:3802—Added cascading devices; 3804, 3806—terminals of a transducerelement to be driven with an H-bridge circuit; 3808—a receive element.In operation, turn on the switch in receive mode (set Txn=1, Txp=0, andthen set Txn=0); 3810—Top plate of transducer, which is automaticallybiased in Receive.

FIGS. 39A-B show an example of a pulser that does not employ a receiveisolation switch, which may be used in some embodiments. The referencenumerals set forth in FIG. 39A-B correspond to the following featuresand/or characteristics of the illustrated layout: 3902—Resistor definedby N-well in Psub or by nonsilicided polysilicon on FOX;3904—High-voltage NMOS pull down device; 3906—Direct connection to RX(no switch yields less parasitics); 3908—Automatic receive bias; and3910—Cascode device for double voltage.

FIGS. 40A and 40B show an example of a time-interleaved single slope ADCand the operation thereof, respectively, that, in some embodiments, maybe employed as one or more of the ADCs reference herein. In theillustrated example, N parallel ADCs are used for one channel to takealternating samples such that the sampling frequency of each ADC is muchlower than the Nyquist criterion. Such single slope ADCs may, forexample, allow large-scale sharing of resources: bias, ramp, and graycounter. Such an ADC approach may thus provide a highly scalable, lowpower option.

FIG. 41 shows an example of a time interleaved sample and hold circuitthat may be employed in some embodiments. In the example shown,reference numeral 4102 signifies a step during which evens are sampled,and then odds are sampled, and reference numeral 4104 signifies a stepduring which the odds are compared, and then the evens are compared.

FIGS. 42A and 42B show an example of a time shared high speed ADC andthe operation thereof, respectively, that, in some embodiments, may beemployed as one or more of the ADCs referenced herein. Such an ADC may,for example, employ a pipelined, SAR, or flash architecture. Because asingle high speed ADC having such an architecture may be used to sampleN channels, such an ADC approach may significantly reduce arearequirements.

The high voltage CMOS circuitry described herein may be configured todrive voltages higher than those conventionally attainable with CMOScircuitry, and to provide high voltages at deep submicron nodes. In someembodiments, voltages up to approximately 10 V may be handled or driven,up to approximately 20 V may be handled or driven, up to approximately30 V may be handled or drive, up to approximately 40 V may be handled ordriven, up to approximately 50 V may be handled or driven, up toapproximately 60 V may be handled or driven, any voltage within thoseranges, or other suitable voltages, as non-limiting examples.

Having thus described several aspects and embodiments of the technologyset forth in the disclosure, it is to be appreciated that variousalterations, modifications, and improvements will readily occur to thoseskilled in the art. Such alterations, modifications, and improvementsare intended to be within the spirit and scope of the technologydescribed herein. For example, those of ordinary skill in the art willreadily envision a variety of other means and/or structures forperforming the function and/or obtaining the results and/or one or moreof the advantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the embodimentsdescribed herein. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific embodiments described herein. It is, therefore, to beunderstood that the foregoing embodiments are presented by way ofexample only and that, within the scope of the appended claims andequivalents thereto, inventive embodiments may be practiced otherwisethan as specifically described. In addition, any combination of two ormore features, systems, articles, materials, kits, and/or methodsdescribed herein, if such features, systems, articles, materials, kits,and/or methods are not mutually inconsistent, is included within thescope of the present disclosure.

The above-described embodiments can be implemented in any of numerousways. One or more aspects and embodiments of the present disclosureinvolving the performance of processes or methods may utilize programinstructions executable by a device (e.g., a computer, a processor, orother device) to perform, or control performance of, the processes ormethods. In this respect, various inventive concepts may be embodied asa computer readable storage medium (or multiple computer readablestorage media) (e.g., a computer memory, one or more floppy discs,compact discs, optical discs, magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other tangible computer storage medium) encoded with one ormore programs that, when executed on one or more computers or otherprocessors, perform methods that implement one or more of the variousembodiments described above. The computer readable medium or media canbe transportable, such that the program or programs stored thereon canbe loaded onto one or more different computers or other processors toimplement various ones of the aspects described above. In someembodiments, computer readable media may be non-transitory media.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects as described above. Additionally,it should be appreciated that according to one aspect, one or morecomputer programs that when executed perform methods of the presentdisclosure need not reside on a single computer or processor, but may bedistributed in a modular fashion among a number of different computersor processors to implement various aspects of the present disclosure.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconvey relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

When implemented in software, the software code can be executed on anysuitable processor or collection of processors, whether provided in asingle computer or distributed among multiple computers.

Further, it should be appreciated that a computer may be embodied in anyof a number of forms, such as a rack-mounted computer, a desktopcomputer, a laptop computer, or a tablet computer, as non-limitingexamples. Additionally, a computer may be embedded in a device notgenerally regarded as a computer but with suitable processingcapabilities, including a Personal Digital Assistant (PDA), a smartphoneor any other suitable portable or fixed electronic device.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audibleformats.

Such computers may be interconnected by one or more networks in anysuitable form, including a local area network or a wide area network,such as an enterprise network, and intelligent network (IN) or theInternet. Such networks may be based on any suitable technology and mayoperate according to any suitable protocol and may include wirelessnetworks, wired networks or fiber optic networks.

Also, as described, some aspects may be embodied as one or more methods.The acts performed as part of the method may be ordered in any suitableway. Accordingly, embodiments may be constructed in which acts areperformed in an order different than illustrated, which may includeperforming some acts simultaneously, even though shown as sequentialacts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively.

What is claimed is:
 1. An ultrasound device, comprising: a semiconductordie having formed thereon: a plurality of ultrasound elements includinga first ultrasound element having at least one first capacitivemicromachined ultrasonic transducer (CMUT) and a second ultrasoundelement having at least one second CMUT; a first programmable waveformgenerator coupled to the first ultrasound element and configured toprovide a first ultrasound waveform to the first CMUT, the firstprogrammable waveform generator having one or more configurableoperating parameters; a second programmable waveform generator coupledto the second ultrasound element and configured to provide a secondultrasound waveform to the second CMUT, the second programmable waveformgenerator having one or more configurable operating parameters; acontroller configured to control values of a first configurableoperating parameter of the first programmable waveform generator and asecond configurable operating parameter of the second programmablewaveform generator; a first analog-to-digital converter (ADC) coupled tothe first ultrasound element and configured to convert an analog signalprovided by the first ultrasound element into a digital signal; a secondADC coupled to the second ultrasound element and configured to convertan analog signal provided by the second ultrasound element into adigital signal; and a digital serial communication module configured tocommunicate a serial digital stream of data that includes the digitalsignals from the first and second ADCs from the ultrasound device to anexternal device.
 2. The ultrasound device of claim 1, wherein thedigital serial communication module is a universal serial bus (USB)module.
 3. The ultrasound device of claim 1, wherein the firstprogrammable waveform generator is programmable to produce a chirp, acontinuous wave, a coded excitation, or an impulse.
 4. The ultrasounddevice of claim 3, wherein the one or more configurable operatingparameters of the first programmable waveform generator include a phase,a frequency, and a chirp rate.
 5. The ultrasound device of claim 1,wherein the first programmable waveform generator is disposed within thesemiconductor die beneath the first CMUT.
 6. The ultrasound device ofclaim 1, wherein the plurality of ultrasound elements comprises at leastsome ultrasound elements configured to provide high intensity focusedultrasound (HIFU).
 7. The ultrasound device of claim 6, furthercomprising a pulser coupled between the first programmable waveformgenerator and the first CMUT and configured to provide voltage pulses tothe first CMUT, at least some of the voltage pulses having a voltagebetween approximately 30 Volts and approximately 120 Volts.
 8. Theultrasound device of claim 6, wherein the first plurality of ultrasoundelements comprises at least some ultrasound elements configured toperform ultrasound imaging.
 9. The ultrasound device of claim 1, furthercomprising a pulser coupled between the first programmable waveformgenerator and the first CMUT and configured to provide voltage pulses tothe first CMUT.
 10. The ultrasound device of claim 1, further comprisinga shift register coupled to an input of the first programmable waveformgenerator and configured to provide a timing control signal to the firstprogrammable waveform generator.
 11. The ultrasound device of claim 1 incombination with the external device, wherein the external devicecomprises a tablet computer.
 12. The ultrasound device of claim 1 incombination with the external device, wherein the external devicecomprises a smartphone.
 13. The ultrasound device of claim 1, whereinthe first ADC forms part of a receive signal path between the first CMUTand the digital serial communication module, and wherein the receivesignal path further comprises a demodulator coupled to the first ADC.14. The ultrasound device of claim 13, wherein the demodulator is adigital quadrature demodulator that is coupled to an output of the firstADC.
 15. The ultrasound device of claim 13, wherein the receive signalpath further comprises a low-noise amplifier (LNA) and a variable gainamplifier (VGA) coupled to an input of the demodulator.
 16. Theultrasound device of claim 13, wherein the receive signal path furthercomprises a decimating low-pass filter coupled to the demodulator. 17.The ultrasound device of claim 13, further comprising an averagingcircuit coupled to an output of the demodulator.